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PodPhantom: A Robotic Prototype Dosimetric Data Collection System for GammaPod

D Parsons*, T Chiu , Y Zhang , W Lu , S Jiang , X Gu , UT Southwestern Medical Center, Dallas, TX


(Sunday, 7/14/2019) 5:00 PM - 6:00 PM

Room: Stars at Night Ballroom 1

Purpose: This work aims to develop PodPhantom, a compact dosimetric data collection system, enabling automatic, accurate, and efficient data collection on a special radiation unit GammaPod.

Methods: PodPhantom is designed to use remote control to automatically move an ion chamber in a cylindrical coordinate, with translation in vertical and horizontal directions and rotation around a mechanical isocenter. Translations are accomplished by automatically movement of stepper motors (51µm step resolution), while rotation is achieved by manually turning the stage along mechanically constructed spokes. A customized plastic jig is fabricated to hold and register the motion stage to GammaPod radiation axes. A cylindrical chamber holder is installed on the motion stage with a home-made plastic block. The motion stage is controlled with a Raspberry Pi microcomputer and wireless connected to a controlling computer from outside the vault. The prototype operates in two modes: a step-and-shoot mode with 30-second integration between for beam scanning and a static positioning mode for point-dose measurement. The performance of PodPhantom was evaluated through initial mechanical assessment and later dosimetry data collection.

Results: Horizontal and vertical straightness were validated by measuring the light field projection of the device against a flat surface and plumb line, respectively, over the range of motion to be less than 0.1 degrees. Positioning and reproducibility of the system was validated using a caliper to be less than 0.1 mm. Profile scanning was conducted in a water-filled breast cup using a Standard Imaging A16 chamber and PTW UNIDOS electrometer. PodPhantom reduced the collection of a single profile from hours to minutes and overall data collection for commissioning from weeks to days.

Conclusion: PodPhantom has been constructed and used in GammaPod commissioning. Future evolution of the system would include automated rotation of the stage and refinement of the existing system.


Commissioning, Data Acquisition, Breast


TH- Radiation dose measurement devices: Development (new technology and techniques)

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